Apparatus for powder metallurgy



March 2, 1948. 1.. D. RICHARDSON APPARATUS FOR POWDER METALLURGY FiledOct. 1, 1945 v n a 3 :1 z r mm M "TR wmmm M r K Y I D D M L 1 f F w 1 1III 1111/ 1/ l \1 1 1 H/ u x souece 0F men FREQUENOI rusc rmcm. eusaev ww w m 1 w x n 1 11 fl1 I/1 1/111 1 1//// Patented Mar. 2, 1 948APPARATUS FOR POWDER METALLURGY Lloyd D. Richardson, Dayton, Ohio,assignor to H-P-M Development Corporation, Wilmington, DeL, acorporation of Delaware Application October 1, 1945, Serial No. 619,654

3Claims.

1 This invention relates to powder metallurgy and particularly, to amethod of and apparatus oiforming workpieces from powdered metal in asingle operation.

The particular object of this invention is to provide an improved methodfor forming and sintering powdered metal workpieces in a single step.

It is another object to provide a method and apparatus for formingworkpieces of powdered metal which fully forms the said workpiecethereby eliminating subsequent machining operationsr It is still anotherobject to provide a method and apparatus for sintering powdered metalparts under pressure whereby the resulting workpiece is fully formed andprecisely sized.

These and other objects and advantages will become more apparent uponreference to the accompanying drawings in which:

Figure 1 is a diagrammatic, sectional view of press adapted forpracticing the method of this invention;

Figure 2 is a perspective view showing a workpiece in the process ofbeing formed; and

Figures '3 and 4 are modified arrangements of the die member of thisinvention.

General arrangement The apparatus for pressing and sintering a workpiecefrom powdered metal according to this invention comprises a mold or diecell formed of low electrical conductivity and preferably nonmagneticmaterial which has sufficient strength to withstand the pressures atwhich the workpiece is formed. The pressing plungers which compress theworkpiece within the die have at least their end portions formed of thesame material so that the workpiece is completely enclosed thereby.Materials which have been found suitable for this purpose include glass,ceramics and in certain instances graphite.

There is disposed around, the die cell a coil which is connected with asource of high frequency electrical energy. The coil establishes a heatproducing alternating field in the workpiece and raises it to sinteringtemperature while under pressure by the plungers. After a predeterminedtime, the sintering operation is completed and the workpiece is cooled.and ejected. A completely finished and accurately sized workpiece isthus produced.

Structural arrangement Referring to Figure 1, there is shown a presshaving a bed l which is connected by strain rods 2 [2 with a head i l,The bed HJ mounts an up ward acting fluid operable plunger l5 whose endportion comprises the glass or ceramic member 18.

The head l4 mounts the fluid operable plunger 20 which has "at its lowerend the glass or ceramic member '22. The members it and 22 arereciprocable in the cavity 24 "of a die cell 26 which is formed of thesame material as the said members.

Mounted about the die cell 28 is a coil 28 which is connected through aswitch 30 with a source of high "frequency ee'lctrical energy indicatedat 3!. Closure of the switch '30 will bring about the energization ofthe coil 2 8 to establish a high frequency alternating held through thedie cell 23. Inasmuch as the die cell '25 and the pressing members 18and 2 .2 are formed of a nonconducting material, the energy of the fieldis absorbed by the metal powder within the cavity 2!.

While it is apparent that any nonconductin'g material having sufficientstrength is suitable for use as the die cell 26 and pressing members I!and 22, it is preferred to employ a high strength glass or ceramic.However, in certain instances graphite may be used in which case acertain amoun'tof heat would be generated in the graphite material whereit touched the workpiece and the heating effect at the surface of theworkpiece would "thus be somewhat enhanced.

In Figure 3, there is illustrated a modified form of die cell 34 whichis strengthened by the addition of a thin metal shell 36 therearoundwhich, while being heavy enough to add strength to the die, is not heavyenough to absorb an appreciable amount of energy from the fieldestablished by the coil 38.

In Figure 4 there is shown a die cell 40 which has imbedded therein acoil 42 for establishing the heating field of electromagnetic inductionin the workpiece in the cavity 44. In Figure 4 the coil 42 is disposed,nearer to the workpiece than is possible with the arrangements shown inFigures l and 3 and in addition provides a support for the die when itis under pressure.

While the method and apparatus of this invention are adapted for formingworkpieces from any powdered metal material, it is evident that it is ofparticular value in connection with the forming of refractory materialswhich are ordinarily too hard to be machine worked after sintering.

Operation In operation, a predetermined quantity of powdered material isplaced within the cavity 24 and the press members 22 and 18 are advancedinto the die cavity to engage the powder with pressing force.Thereafter, the switch 30 is closed to energize the coil 28 thereby toestablish an alternating field of electromagnetic induction been raisedsufficiently high the switch 30 is opened while the pressure of thepressing memhers on the workpiece is continued, After the workpiece hasbecome fully sintered and is cooled sufficiently to permit its ejectioninto the atmosphere, the pressing member 22 is withdrawn while themember I8 is actuated to force the finished workpiece from the die. Byproperly concavity; motor means for actuating said plungers forcompacting the material within said die and for ejecting the finishedworkpiece from said die, said die and at least the end portions of saidplungers being substantially electrically non-conductive; an inductioncoil adapted when energized for establishing a magnetic fiield throughthe material within said die; and a source of high frequency electricalenergy adapted for connecting to said coil; means for supporting one ofsaid pressing plungers in spaced relation from said bed comprisingstrain rods, said bed having means for supporting said other pressingplungers, and means for reciprocating said presstrolling the amount ofmaterial placed into the die and by properly shaping the die andplungers, the ejected workpiece may be controlled as to the size andshape so as to require no subsequent machining operation,

While the apparatus disclosed and described herein constitutes apreferred form of my invention, it will be understood that the apparatusis capable of alteration without departing from the spirit of theinvention, and that all modifications that fall within the scope of theappended claims are intended to be included herein. v

I claim:

1. In an apparaus for forming workpieces from powdered metals; asubstantially horizontal bed; a die of substantially electricallynon-conductive material supported on said bed; an opposed pair ofpressing members reciprocable in the cavity of said die and comprisingat least end portions which are substantially electricallynon-conductive; and an induction coil encircling the cavity ofsaid dieand adapted for being energized by a source of high frequency electricalenergy; means for supporting one of said pressing members in spacedrelation from said bed comprising strain rods, said bed having means forsupporting said other pressing member, and means for reciproeatin saidpressing members com-prising cylinders and pistons mounted on saidstrain rods and bed respectively.

2. In an apparatus for forming finished workpieces from metal powders; asubstantially horizontal bed; a die supported on said bed having acavity, a pair of plungers reciprocable in said ing plungers comprisingcylinders and pistons mounted on said strain rods and bed respectively.

3. In an apparatus for forming finished workpieces from metal powders; asubstantially horizontal bed; a die supported on said bed having acavity, a pair of plungers reciprocable in said cavity from oppositesides thereof; motor means for actuating said plungers for compactingthe material within said die and for ejecting the finished workpiecefrom said die, said die and at least the end portions of said plungersbeing substantially electrically non-conductive; an induction coiladapted when energized for establishing a magnetic field through thematerial within said die; and a source of high frequency electricalenergy adapted for connecting to said coil, means for supporting one ofsaid pressing plungers in vertically spaced relation from said bed, saidhe'd having means for supporting said other pressing plunger, said motormeans including means for reciprocating said pressing plungers andcomprising cylinders and pistons mounted on said supporting means andbed respectively.

LLOYD D. RICHARDSON.

REFERENCES CITED The following references are of record in the file ofthis patent:

UNl'I'ED STATES PATENTS Number Name Date 1,380,250 Reymond May 31, 19212,225,424 Schwarzkopf Dec. 1'7, 1940 2,293,400 Morris et a1. Aug. 18,1942 2,384,215 Toulmin Sept. 4, 1945 2,393,130 Toulmin Jan. 15, 1946

